Network help - ethernet port wouldn't show up in Network preferences summary.

At home, I have AirPort Extreme, so I connect to the net with my wireless card. But when I came back to college, I use an ethernet cable, because their wireless network is unreliable. But when I plugged it in, nothing happens, and when I checked Network in System Preferences, the summary only shows AirPort and Internal Modem. How can I get the computer to see the ethernet cable? It was working fine in December before I left.

I'm now using their wireless network, but who knows how long it'll stay up.

ethernet should only show up there if its plugged in and connected to something. i say something because even if the internet isnt working through it it still shows up with a red status dot. sounds like one of three things:
1) their network or wall plug is messed up
2) your cable is broken
3) your network port is broken

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